The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: tunnelrider on August 30, 2015, 04:05:18 AM
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This must be a common question sorry, I searched the FAQ's and tried the search tool numerous times, love the forum thou!
Now would be the perfect time to fit a better 5th if it hasn't already got one, is it better though?
Also how many teeth? Should probably ask the shops but you guys are way quicker!
Thanks for any info,
Dan
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I don't have one but I know only one of the pinions is replaced so it's a special gear wheel that retains the same diameter but is 1 tooth different. It must be tricky enough engineering to pull that off so there must be no chance it could be made 2 teeth different.
Here's a quote from Anton Largiader who is highly respected in airhead circles
I don't know anyone who has had a problem with the tall 5th gear. If it works for the type of riding you do, get it. I've installed about 15 of them in the past few years.
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Now would be the perfect time to fit a better 5th if it hasn't already got one, is it better though?
Yes, now would be the time!
Most bikes I've owned have suffered from short gearing on top. Designed for performnce and not economy. I had a 1200 Bandit that could have had 3 more gears on top, maybe it would have made better mileage than 27 mpg.(yuk)
Everything I have heard says it is a fine mod. I have a taller rear drive on the shelf to install someday on the R65
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How much of a difference, will one extra tooth on the gear make ???
What's the cost of the new gear ???
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It is only a 5% increase in speed at any given RPM.
3mph increase at 60 mph.
I think it would be nice to have on the straights but on the curvy parts not sure it is worth it.
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At common highway speeds, the difference between 4th and 5th is no more than 500 RPM. Another 5% would definitely make it more of an overdrive and a more relaxed, longer legged stretch for the flat roads. You might find you need to use 4th a little more often on the hills - the one thing I find is that the R65 doesn't do too badly for overtaking in 5th gear provided I've got enough roadway to work with.
Even though it feels short-legged, I generally don't have any problems getting 44-48 MPG on my LS, which has the lower ratio rear (32/9) provided I keep the speeds below about 120 km/h
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I find the normal 5th works fine, but I go for a taller gear in top just to relax the motor at motorway speeds, and it might help shift the handlebar buzz out of my usual 65-75mph motorway cruising speed.
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I have put 30,00 kilometers on my 1986 R65 since installing the taller 5th gear. For me it has been a great upgrade.
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I have just stumped up the money for a high ratio 5th gear so I should be in a position to report on it by about Christmas. I can say that I did briefly fit (with a view to purchase) a 32:10 final drive.
My perspective is that my 1984 R65 has very little bottom end, due I suspect in equal parts to a lack of flywheel weight (clutch carrier model) and a lack of compression due to the 1979 model pistons fitted.
Some here may recall that I put a 1984 and 1979 piston side by side with the ring lands interlocked (using one set of piston rings) and established that the 1979 piston is approximately 1.5mm lower in deck height.
In any event the results with the higher ratio rear drive were not pleasant and the poor thing noticeably struggled to get off the line, particularly where the start was uphill. I did buy the final drive anyway, it is destined for the wife's bike which has a healthy R80 still running R65 gearing.
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Thats the beauty of the higher 5th gear, it doesn't effect the lower gears so your riding 1st through 4th is unchanged. My 1986 comes standard with a 3.36 rear end so it is taller than the earlier r65s ,when I changed the 5th gear it gives me a 3.2 final drive in 5th. The bike pulls this higher 5th at highway speeds with no problems , drop down to 4th for quicker passing .